PERIODIC TABLEPERIODIC TABLEPeriods go across:

1st period H He2nd period Li Ne3rd period Na Ar

Groups go down:

1st group Alkali Metals Li Fr2nd goup Alkaline Earth Metals Be Ra…Last group Noble/Inert Gases He Rn

RELATIVE ELECTRONEGATIVITIESUp and to the right: electronegativity increases.(same trend for ionization energy & electron affinity)

RELATIVE SIZESDown and to the left: size increases.

Smallest sizeHighest EN

IE EA

Largest sizeLowest EN

IE EA

Metallic Character

Most elements in the periodic table are metals

- metals lose electrons- good thermal and electrical conductors- malleable and lustrous

- non-metals gain electrons- gas, liquid, or brittle solid- poor conductors

increasing metallic character

OXIDATION STATESAtoms tend to lose or gain electrons to achieve an inert gas configuration.

Elements to the right (e.g., O, F) are electronegative gain electrons to become negatively charged (anions).

Elements to the left (e.g., Cs, Sr, Al) are electropositivelose electrons to become positively charged (cations).

NaCl Na+Cl

MgO Mg2+O2

For main group (s- and p-block) elements:The highest possible positive oxidation state is equal to the Group Number

AQUEOUS SOLUTIONS

Metals lose electrons to form cations in aqueous solutions (e.g, Ba2+)

Non-metals gain electrons when forming anions in solution (e.g., Br-).

Non-metals can also lose electrons to more electronegative elements, as in oxyanions:

e.g., in SO42-, oxidation states are S6+, O2-

OXIDES

Metal Oxides and Hydroxides are basic more soluble in acidic solutions.

More electropositive central atom gives off electrons (Na+ OH-)

Non-Metal Oxides and Hydroxides are acidicmore soluble in basic solutions.

More electronegative central atom attracts electrons (HNO3 NO3

- + H+)

Metalloid Oxides and Hydroxides are amphotericMore soluble in both acidic and basic solutions compared to pure water.

2nd row (Li,Be…F) vs. 3rd, 4th, 5th rowsPeriod II:Small atomsThe only valence orbitals are 2s and 2p No 2d orbitals Maximum number of bonds = 4.

CF4, NH3.Small size a greater tendency to form bonds because there is better sideways overlap of p-orbitals.

Period III: Bigger size. Valence orbitals: 3s, 3p, and 3d.

Maximum number of bonds > 4.SiF4, SiF6

2-, PCl3, and PCl5.Bigger size less tendency to form bonds because there is less overlap of p-orbitals.

2nd row (Li,Be…F) vs. 3rd, 4th, 5th rows

HydrogenProperties

diatomic gas colorless, odorlesstasteless

most abundant element in the universe

rare in its elemental state on earth (it escapes from the atmosphere).

Common Oxidation States

0, +1, -1

Steam reforming (current method of H2 production)CH4(g) + 2 H2O(g) CO2(g) + 4 H2(g) (natural gas)

Uses Ni catalyst at 800oCCarbon monoxide (CO) is made as a byproduct.

water gas shift (converts CO at 300oC using Cu catalyst) CO(g) +H2O(g) CO2(g) + H2(g)

Hydrogen - Sources

Other methods electrolysis of water (clean but uses too much energy)

2 H2O(l) 2 H2(g) + O2(g)

reactions of active metals (lab scale method) H2SO4(aq) + Fe(s) H2(g) + FeSO4(aq)

steam reforming of carbonC(s) + 2 H2O(g) CO2(g) + 2 H2(g)

high temperature catalytic process, coal is the source of carbon.

1H protium most abundant isotope, nucleus consists of a single proton

2H deuterium one neutron and often given the symbol “D”. forms the hydrogen component of heavy water (D2O).

3H tritium radioactive isotope: half-life of 12.3 y, not found in nature.

Isotope effects Deuterium and hydrogen exhibit isotopic differences in their reaction rates and properties.

E.g., boiling points of heavy water and conventional water are slightly different allowing them to be separated by fractional distillation.

Hydrogen Isotopes

Main use of H2 in US Haber-Bosch process N2(g) + 3H2(g) 2 NH3(g)

synthetic fertilizers: (NH3) can also be further reacted to produce nitrate (–NO3) compounds.

Other Uses: Production of methanol

CO(g) + 2H2(g) CH3OH(l)

HydrogenationCH2 CH2 CH3 CH3

converts double bonds into single bonds: unsaturated compounds like oils into saturated fats.

Hydrogen - Commercial applications

Molecular hydrides

hydrogen bonded covalently to another element.

Examples: HCl, HBr, NH3,CH4, Al2H6… exist as molecules (in gas, liq., solid)

acid strength increases from left to rightPH3 < H2S < HCl

bond strength decreases going down family H2O < H2S < H2Se < H2Te (least stable)

Hydrogen Compounds

Ionic Hydrides: hydrogen and an alkali metal such as lithiumExamples: NaH (=Na+H-), CaH2

strong bases, strong reducing agentsreact with water or acids to make H2

Molecular Hydrides: hydrogen and a non-metalExamples: NH3, H2O, HCl

covalent bonding

Metallic hydrides hydrogen and a transition metal. retain their metallic characteristics hydrogen atoms are absorbed into the interstices of the metal atomic lattice.

ACTIVE METALS - GROUPS I AND II

Group I Group II

Family Alkali Metals Alkaline Earths

Electronic config. ns1 ns2

Oxidation State +1 +2

Melting Point Low Higher

Bonding Ionic Ionic (except Be)

Oxides, hydroxides Basic Basic (exc. amphoteric Be)

Electropositive Most Yes

Very Reactive  React with Air, Water

In many compounds, Li+ resembles Mg2+ rather than Na+.

Examples:Li2CO3 and MgCO3 are virtually insoluble in water, while Na2CO3 is very soluble.

Ionic Radii: Li+ 0.60Å

Na+ 0.95Å Mg2+

0.65Å

DIAGONAL RELATIONSHIPS

CHEMICALS FROM NaCl

Na metal is obtained by molten salt electrolysis of a 40:60 mixture of Na/Cl/CaCl2.

This mixture melts at 580°C vs. 800°C for pure NaCl.

Cathode: 2Na+ + 2e- 2Na (l)

Anode: 2Cl- Cl2(g) + 2e-

2Na+ + 2Cl- 2Na (l) + Cl2(g)

NaOH (caustic soda).

>20,000,000,000 pounds made anually by electrolysis of aqueous NaCl (chlor-alkali process).

Cathode: 2H2O + 2e- H2(g) + 2OH-

Anode: 2Cl- Cl2(g) + 2e-

2H2O + 2Cl- H2(g) + Cl2(g) + 2OH-

2Na+ + 2OH- (=2 NaOH) is left behind.

NaOH dissolves hair and skin (e.g., Drano).

Uses: Soap, Rayon, Cellophane, Paper, Dyes.

ALKALINE EARTHSALKALINE EARTHS

Mg, Ca, Sr, Ba compounds are ionic; hydroxides are basic.

Metals are obtained by high temperature electrolysis of their molten chlorides.

Mg metal is made in three steps from sea water:

1) Add base to sea water: Mg2+ + 2OH- Mg(OH)2(s)

2) Dissolve in HCl: Mg(OH)2(s) + 2HCl MgCl2(aq) + 2H2O

3) Electrolysis: MgCl2(l) Mg(l) + Cl2(g)

Principal Uses of Mg: Light structural alloys (lighter than Al or Fe, but strong). Light alloys with Zn, Al, or Mn for aircraft wheels, space vehicles, portable tools, and cameras

BERYLLIUMRare element - 0.0005% of the earth’s crust is Be

Source: The mineral beryl is Be3Al2Si6O18 has different colors due to trace impurities if light blue-green = aquamarine if deep green = emerald

Uses:Nuclear reactor parts – strong but transparent to neutronsX-ray tubes have Be windowsBe is strong and relatively light and is transparent to X-rays.

Be compounds are covalentBe(OH)2 is amphotericSimilar to Al (diagonal relationship)

The twelve most abundant elements in the lithosphere:

Element Percent by weightOxygen 50Silicon 26Aluminum 7.5Iron 4.7Calcium 3.4Sodium 2.6Potassium 2.4Magnesium 1.9Hydrogen 0.9Titanium 0.6Chlorine 0.2Phosphorus 0.1

CALCIUMFifth most abundant element on earth.

CaCO3

Depending on form is limestone, marble, chalk.Bones and teeth are largely CaCO3 and Ca3(PO4)2

Tooth Enamel = Ca10(PO4)6(OH)2 = Hydroxyapatite

Cavities: Ca10(PO4)6(OH)2 + 8H+ 10Ca2+ + 6HPO42- + H2O

Fluoride replaces OH- with F-.F- is a weaker base, so it reacts less with acid.

CaCO3(s) + Heat CaO(s) + CO2(g) (Lime)Very important industrial chemical (steelmaking, concrete).

CALCIUM (cont’d)CaSO4 . (H2O)2 (Gypsum) is used to make cement and plaster wallboard.

2 CaSO4. (H2O)2 + Heat 3H2O + (CaSO4)2 . (H2O)

(Plaster of Paris)Reverse reaction by adding water.

BARIUMBarium is very dense.

BaSO4 is a dense, very insoluble material used as an additive to concrete in nuclear reactors. This makes the walls more dense. This also makes the walls absorb neutrons.

BaSO4 also absorbs X-rays - used by radiologists for stomach X-rays.

WATER SOFTENINGWATER SOFTENINGHard water contains dissolved Ca2+ and Mg2+.

These form precipitates with soap – bath tub rings. Most detergents do not work well to remove this.Also forms deposits in water pipes.

Ca2+(aq) + 2HCO3-(aq) CaCO3(s) + CO2(g) + H2O

from dissolved CO2 scale

Scale forms on the bottom of teapots, in faucets, on the walls of hot water pipes and boilers, etc.

Can be removed with acid (e.g., vinegar)